1. Field of the Invention
This invention relates to an ultrasonic device for cleaning a venturi flow nozzle mounted in a pipe in a fluid system whereby the nozzle may be cleaned on line without requiring the system to be shut down.
2. Description of the Prior Art
In operation of many industrial plants employing fluid systems having venturi flow nozzles therein, fouling of the venturi flow nozzles, particularly at or near the throat, occurs causing the flow indication to be higher than the actual or calibrated flow value. In these circumstances, the flow rate is less than actually indicated, and consequently, the output for the plant is reduced. This is particularly true in connection with pressurized water nuclear powered electric generating plants which employ venturi flow nozzles in the main feedwater pipe to measure the flow rate of the feedwater to the steam generator. In such plants, following the secondary side calorimetric and adjustment of the Nuclear Instrumentation System, indicated power is higher than the actual reactor power, and the plant thus operates below its licensed thermal limit. Because of this, the electrical output on such plants can fall short of its rated limit by as much as four percent, which in some plants can amount to 40 megawatts.
While various means have been tried for correcting the problem of fouling of venturi flow nozzles, none have proved totally satisfactory. For example, one solution has been to install a handhole upstream of the venturi flow nozzle and manually insert a jet spray nozzle through the handhole to hose off and remove deposits for fouling on the inner surface of the venturi. This particular solution requires a plant shutdown and pipe drainage which is expensive and time consuming. Another solution has been to install leading edge flow meters which are not subject to fouling. Installation of such leading edge flow meters, however, can be expensive.
At the present time, numerous utilities with nuclear power plants, in particular, are trying to find solutions to recovering lost megawatts due to feedwater venturi flow nozzle fouling. In view of the fact that a good solution to the fouling problem presently does not exist, such utilities are reluctant to implement any solutions, and consequently, they continue to lose megawatt output which is very costly.
Accordingly, a need still exists for an economical device capable of easily cleaning venturi flow nozzles which is relatively inexpensive and easy to install and which does not require plant shutdown and pipe drainage.